One of the greatest mysteries of the universe is that the endless trillions of stars are not evenly scattered throughout outer space. No, stars are grouped into galaxies, just as people gather in cities, leaving the spaces between them unoccupied. The name of our Galaxy is the Milky Way. It is a huge, rotating flat disk made of gas, dust and about 200 billion stars. The distance between neighboring stars in the Galaxy is trillions of kilometers of empty space. Our Sun, one of the many stars that inhabit the Galaxy, is located on its periphery.
Milky Way Galaxy
When we look into the night sky, we look through the stars, like through raindrops adhering to a window pane. All of the individual stars that we see in the sky belong to the Milky Way. Our Galaxy has a spiral shape. From above, it looks like a whirlwind of stars. Stars revolve around the center of the Galaxy, as planets revolve around stars. It takes the Sun about 200 million years to complete one revolution in this stellar carousel, and it moves at a speed of no less than 940,000 kilometers per hour. From the side, the Galaxy looks like a disc with an elevation in the center. The bright white stripe that crosses the sky on a clear night is part of this disc.
Other galaxies
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This is how we see our Galaxy. If we could get out of it, we could see the Universe in all its pristine beauty: a huge impenetrable - black space, over which brightly lit galaxies are scattered, like illuminated islands in the night sea. The Milky Way itself is a huge space formation, but it is only one of the 100 billion galaxies available for observation in space. Although each galaxy is a cluster of millions of suns, they are located so far from us that they are perceived as rather faint nebulae. Several dozen galaxies can be viewed with a small telescope. Well, if you use the most modern powerful telescope, you can not only see many galaxies, but also see individual stars in some galaxies.
Andromeda Nebula Galaxy
On a very clear night, it is sometimes possible to make out the Andromeda Nebula galaxy, the Milky Way's closest neighbor. Moreover, this does not require any optical device. Just like the Milky Way, the Andromeda Nebula is a spiral. More than half of all galaxies are spiral in shape. Such galaxies, similar to a village spinning wheel, contain new, old and middle-aged stars.
Galaxies of a different shape
There are elliptical galaxies. These are huge, rounded balls of billions of stars. Some of these galaxies are nearly perfectly round, others are slightly flattened. In elliptical galaxies, stars revolve very closely around the center, resembling a swarm of bees. Most often, elliptical galaxies are made up of old stars, many of which are red giants. Therefore, elliptical galaxies almost always glow red or orange. There are galaxies and other forms. There are galaxies that resemble a biconvex lens, or spiral galaxies without thickening in the center. There are galaxies that don't have any shape at all. Such galaxies are called irregular.
Accidents with galaxies
While the galaxies look like peaceful and serene clusters of stars from the perspective, their appearances can be quite deceiving. These worlds are the arena of the strongest natural shocks, the galactic equivalent of earthquakes and volcanic eruptions. Here's a modern example. From the center of the galaxy M87 there was a monstrous ejection of blue - white incandescent gas. A huge amount of energy was released into space. The fiery tongue of the ejected gas is about 5,000 light years long. Scientists think the black hole in the center of the galaxy, swallowing up cosmic dust and entire stars, is the source of this eerie - majestic spectacle.
Collisions of galaxies
Sometimes galaxies collide with each other. Since there is a lot of empty space between the stars of galaxies, galaxies usually freely pass their own way, without "noticing" collisions. Due to the enormous size of galaxies, such collisions do not last for several minutes, but for several million years. Scientists in such cases simulate a collision on a computer. Thus, it is possible to show what happens when galaxies come into close contact, and how they will look after it. When one galaxy invades another, they begin to act on each other with their gravitational fields. In this case, the stars are displaced from their previous positions, destroying the original shape of the galaxy. For example, the curl of a spiral galaxy may stretch towards an approaching elliptical galaxy. Two galaxies can merge after collision,forming a new galaxy larger than the two original ones.
Formation of galaxies
Some scientists suspect that today's impossibly large galaxies were formed from the merging of smaller star clusters. For example, an elliptical galaxy can form from the merger of two spirals. Now galaxies are available for observation, distant from us for 2 million light years. This means that astronomers see galaxies as they were 2 million years ago. So, the more ancient galaxies we see, the smaller they become. Moreover, small ancient galaxies are usually shapeless. Scientists believe that 10 to 100 small galaxies must merge to form a spiral galaxy like our own Milky Way.
